1. Field of the Invention
The present invention relates to a method and apparatus for verifying if a train block signal system is properly designed. More specifically, the invention relates to a method and apparatus for verifying if the actual braking distance of a train moving under specified conditions is less than or equal to the estimate utilized in creating the block design.
2. Description of the Prior Art
The movement of trains along a train track is classified as having a "single degree of freedom," i.e., the train may move only backwards or forwards on the track. In order for the railroad to operate efficiently and cost-effectively, it must maximize the number of trains running along a given section of track during a given period of time. At the same time, safety considerations regulate the ability of the railroad to have trains running in opposite directions, or narrowly spaced apart in the same direction, along this section of track. In order to compromise and achieve maximum utility from the equipment without risk to the operators passengers and freight carried by the train, a system of signaling and braking has been developed.
The signalling system is based on the concept of "blocks." A length of train track is divided into sections, identified as blocks. Signals are provided at the entrance to each block, indicating whether the block ahead is clear for the train to continue. Additionally, the rate that the train may move through the block is displayed. In order to provide further advance warning of block conditions, signals may be posted several blocks in advance, coupled with a clear system identifying which signals are associated with which blocks.
The blocks are laid out by considering the condition of the terrain and the stopping distance of the trains passing through the block. Of course, terrain conditions directly affect the trains' ability to stop. By carefully calculating the length of the blocks and providing proper signalling, the amount and speed of traffic along a stretch of track can be greatly increased from a bare section through which only one train can pass at a time.
As previously mentioned, the critical parameter in block design is the stopping distance of the trains which will pass through the block. The entire system is premised on the condition that the train, given a signal at the entrance to the block, can stop within the block. Another precondition is that the train must be travelling at the proper speed when entering the block. It is therefore necessary to test each block under operating conditions to determine whether a train can stop therein.
As currently practiced, the testing of each block is a long and laborious process. A representative train is outfitted with cargo and placed on the track to be tested. The track is cleared to avoid any collisions. The train is then taken up to speed prior to the entry to the block in question. After entering the block, the train's brakes are engaged for a full service application. The train then comes to a halt. If the train is past the end of the block, the block is obviously too short. If the train is still within the block, the distance to the end of the block is measured. This is then compared to a standard to determine if the cushion between the train and the end of the block is large enough. During this operation, the train may be outfitted with a graphic recorder of its speed and motion to assist in later calculations of movement and distances. In any case, the process is laborious in that the speed and distances must be manually calculated from this data. Furthermore, each block must be individually tested.
There exists, therefore, a need in the art for a computer operated system which can automatically track the speed and motion of the train, and furthermore calculate the cushion between the end of the block and the train. This data could the be compared to the standard, which is also input to the computer, and a numerical and graphic result would demonstrate the operability of the track and block design for service.